Flyback converters are commonly used as isolated power supplies for electronic devices. For example, a flyback converter typically includes two coils that are electromagnetically coupled with each other, like primary and secondary windings of a transformer. The primary coil is coupled to an input circuit/power source, and the secondary coil is coupled to an output circuit/load, thus providing desired isolation between the input and output. By controlling a flow of current through the primary coil using a primary switch, a flyback converter may produce a regulated output voltage of a desired target value at the output.
The primary and secondary coils may have parasitic leakage inductances that also capture energy (“leakage energy”). The leakage inductances may cause additional losses unless the energy stored therein is recovered. Thus, some form of leakage energy recovery circuitry may be included in a flyback converter. Additionally, a drive toward miniaturization and portability in the consumer electronic industry pushes such power converters to be packaged in smaller and smaller volumes. Simply decreasing the size and/or component count, however, typically makes it harder to achieve a desired level of efficiency, because operations at high switching frequencies that can facilitate miniaturization may otherwise negatively affect efficiency. Thus, what is needed is a flyback converter adapted to recover the leakage energy to improve efficiency that also provides flexibility to avoid operating at unnecessarily high frequencies.